/*
 * Alloy Analyzer
 * Copyright (c) 2002 Massachusetts Institute of Technology
 *
 * The Alloy Analyzer is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * The Alloy Analyzer is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with the Alloy Analyzer; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

package alloy.ast;

/**
 * A visitor which facilitates replacing nodes in the AST.
 * The default behavior is to replace each child of an AST
 * node with the return value of the invocation of <code>visit()</code>
 * on that node.
 */
public class ASTDepthFirstReplacer extends ASTDepthFirstReturnVisitor {

	/**
	 * Visit a node.  Replace each child of the node
	 * with the return value of the invocation of <code>visit()</code>
	 * on the child, and then return the node.
	 */
	public Object visit(Node node_) {
		for (int i = 0; i < node_.numChildren(); i++) {
			Node child = node_.childAt(i);
			Node newChild = (Node)child.applyReturnVisitor(this);
			if (child != newChild) { // child object has changed
				node_.setChild(i, newChild);
			}	
		}
		return node_;
	}
}

